What is an acceptable speed on a public road?

[cheshirecat]

Many years ago I took a motocycle advanced course run by some UK Police Bikes. We were grouped into about five with a police bike front and rear. The ground rules were to stay within the law but to ride assertively. When they said within the law they meant it. The centerline of the tyre wasn't to cross the yellow line meaning the centerline of the tyre could touch but not cross to within a fraction of an inch. This at 70mph through sweeping bends. This was real precision riding learning very quickly to take pride in our roadcraft and precise interpretations of the law. It was also great being escorted by blue flashing lights overtaking traffic.
I'm still utilising this course today and it provided the foundtions to being able to survive three years of despatch riding in London when several of my fellow riders didn't. I believe the philosophy was that one might survive the odd blast occaisionally( and we've all done the odd blast, being human after all) but one day you'll be caught out

[cheshirecat]

Many years ago I took a motocycle advanced course run by some UK Police Bikes. We were grouped into about five with a police bike front and rear. The ground rules were to stay within the law but to ride assertively. When they said within the law they meant it. The centerline of the tyre wasn't to cross the yellow line meaning the centerline of the tyre could touch but not cross to within a fraction of an inch. This at 70mph through sweeping bends. This was real precision riding learning very quickly to take pride in our roadcraft and precise interpretations of the law. It was also great being escorted by blue flashing lights overtaking traffic.
I'm still utilising this course today and it provided the foundtions to being able to survive three years of despatch riding in London when several of my fellow riders didn't. I believe the philosophy was that one might survive the odd blast occaisionally( and we've all done the odd blast, being human after all) but one day you'll be caught out

[kiwifruit]

Back once again with the ill behavior

[_Shrek_]

You've had 4 cops ... or 4 tickets ... ???

wouldn't you like to know

[racefactory]

It doesn't matter, there is no point exceeding the speed limit on a straight... don't tell me that's actually fun or rewarding? It's the corners that count and if you can get around those pulling some good G and not breaking the speed limit then that's all you need for fun.

Go to lonely track road on the north shore and if you break the 70kmh speed limit significantly around those corners then I'll give you a medal. My favourite place for a short spirited ride.

[The Pastor]

It doesn't matter, there is no point exceeding the speed limit on a straight... don't tell me that's actually fun or rewarding? It's the corners that count and if you can get around those pulling some good G and not breaking the speed limit then that's all you need for fun.

Go to lonely track road on the north shore and if you break the 70kmh speed limit significantly around those corners then I'll give you a medal. My favourite place for a short spirited ride.

that road is really busy and dangerous place to speed.

[racefactory]

that road is really busy and dangerous place to speed.

It's not speeding, it's staying within the 70kmh speed limit. It's also not busy at all... rarely come across a car there on a weekday. Must be thinking of another road? I did mean mainly Wright rd but Lonely track just turns into it.

[The Pastor]

speeding has NOTHING to do with the little sign on the side of the road. you try stoping mid corner at 60ks when a cyclist / suv or kid suddlenly apperares, and then i'll give you the medal.

[BoristheBiter]

speeding has NOTHING to do with the little sign on the side of the road. you try stoping mid corner at 60ks when a cyclist / suv or kid suddlenly apperares, and then i'll give you the medal.

I will take that medal but I will settle for a clean pair of undies.
Mid blind corner looking at the front of a land cruiser. still have no idea how he didn't hit me.
45 on the corner, 70 on the clock would have meant nothing if i became a hood ornament

[BoristheBiter]

It's not speeding, it's staying within the 70kmh speed limit. It's also not busy at all... rarely come across a car there on a weekday. Must be thinking of another road? I did mean mainly Wright rd but Lonely track just turns into it.

I would say that going down Wright road should be part of any bike training.

[Horney1]

I will take that medal.... .
Mid blind corner looking at the front of a land cruiser. still have no idea how he didn't hit me.
45 on the corner, 70 on the clock would have meant nothing if i became a hood ornament

Yep, been there, done that to. Was going legal on a sealed highway (after getting pulled over for a ticket) & had to squeeze past an oversteering landcruiser on a bridge. He (she) had taken a sweeping right dip a bit fast. So, if I was going faster I wouldn't have encountered that one and I would have been on the bridge for less time... (NB - stopping or slowing down would have invited a higher possibility of being where they were going!)

[Ixion]

It's not speeding, it's staying within the 70kmh speed limit. It's also not busy at all... rarely come across a car there on a weekday. Must be thinking of another road? I did mean mainly Wright rd but Lonely track just turns into it.

Now, this post and its predecessor very nicely encapsulate why we have such a high biker road toll.

The single most common cause of fatalities and serious injuries on motorcycles, is a single vehicle crash, where the motorcycle leaves the road on a corner.

Here, we have the poster condemning those who exceed the speed limit in a straight line, whilst advocating riding as fast as possible through corners, on a road known to be treacherous.

He suppoorts the safety of this on the basis that it is not exceeding the speed limit.

So, for him (and it is an idea shared by many), to ride at a speed that is in excess of an arbitrary limit, yet far below the maximum speed possible, is dangerous.

Whereas , to ride at a speed that is less than that arbitrary limit, but deliberately to seek to be right on the edge of the maximum speed possible, is safe. Because "it's less than the speed limit"

The problem is, of course, that a rider riding on the raw edge of maximum possible speed, will sooner or later, go just that little bit *over* the edge. He is *at* the limit. It only needs a misjudgement of a couple of kph. And then we have another statistic.

While the rider riding at 120kph on the straight road probably ahs a spare 100kph in hand before he gets into trouble.

I have a question for all those who cry that "exceeding the speed limit is dangerous". Do you also obey the speed signs on corners? Those yellow ones. Because if you genuinely believe that exceeding an officially recommended speed is inherently dangerous- well, those yellow signs are officially recommended maximum safe speeds also.

The speed on the yellow sign is the maximum that officials believe safe on that corner. If you exceed that speed you are (by your argument) riding dangerously.

[FJRider]

The speed on the yellow sign is the maximum that officials believe safe on that corner. If you exceed that speed you are (by your argument) riding dangerously.

I have noted on a few occasion when some have posted about their bin on a corner, a corner they state they have taken at speeds in excess of that they were travelling at the time (of their bin). It only takes a bit of grit/gravel, an oil/diesel patch, or smooth seal ... and its all over rover ...

After a few "white knuckle moments" on various rides ... I have gone back and had a look at the piece of road this occured, sometimes just a shoddy patch-seal job is the cause.

In short ... even posted warning signs are a guide ... sometimes ... in some conditions/times ... still unsafe.

If you believe it's safe because a sign tells you its safe ... good luck ...

[Mikkel]

I recall reading about reaction times of formula one drivers ... around .25-.35 of a second. With reaction times of around .4 .5 of a second about average/good. This means that on a good day ... at 120 km/hr, you will cover around 33 metres Before you actually start the process of reacting to the situation. Be it braking or "mere" avoidence of the problem that has appeared.

v = 120 km/h = 33.3 m/s

dx = v*dt <=> dx = 33.3 m/s * 0.5 s = 16.7 s

Which means that anything that appears that is closer than 50 metres you will hit AT that speed ... before you react at all. How long will it take YOU to stop from 200 km/hr ... UNDER 50 metres would be GOOD. Which rule of thumb means ... that at 200 km/hr ... anything ahead of you out to 100 metres ... you have a GOOD chance of hitting (and ONLY if that object is NOT moving towards you).

v0 = 200 km/h = 55.6 m/s
v1 = 0 km/h = 0 m/s
dx = 50 m

a = (v1^2 - v0^2)/(2*dx) = - (55.6 m/s)^2/(2 * 50 m) = -30.9 m/s^2 = - 3.2 g

I.e. stopping from 200 km/h in 50 m isn't just GOOD, it takes some really really sticky tyres. (That's me being sarcastic - it's not going to happen by friction braking dependent upon the earth's gravitational pull.)

Stopping distances from 200 km/h fall into the category:

a < 1 g = 9.8 m/^2

dx = (v1^2-v0^2)/(2*a) <=> dx > 157.7 m

I.e. expect to spend more than 157.7 meters if you want to stop from 200 km/h.

NB - this of course doesn't take aero-braking into account.

[FJRider]

I.e. stopping from 200 km/h in 50 m isn't just GOOD, it takes some really really sticky tyres. (That's me being sarcastic - it's not going to happen by friction braking dependent upon the earth's gravitational pull.)

Stopping distances from 200 km/h fall into the category:

a < 1 g = 9.8 m/^2

dx = (v1^2-v0^2)/(2*a) <=> dx > 157.7 m

I.e. expect to spend more than 157.7 meters if you want to stop from 200 km/h.

I was being a "tad" optimistic .... but the aim of my post was to get some on site ... doing their sums on the subject of braking distances. IT WORKED ...

Distance markers (from corners) on race circuits were mentioned as a guide in another post ... but seldom to race tracks require complete stops on each(any) corner ...

Factor in another vehicle travelling towards you at 100 km/hr ... then do the sums ...

If you are moving at 200 km/hr ... a lot of clear road is required to stop ... safely.

Changing your line to avoid a moving object that you cannot predict direction of its travel (car ... sheep etc) is at best .. not always a good option ... at that speed.